This invention relates to flexible gas-insulated cables, and more specifically relates to a novel insulator structure for supporting a high voltage conductor within a flexible outer housing which is filled with electronegative gas. Insulators for flexible gas-insulated cable are well known in the art and typically are shown in U.S. Pat. Nos. 4,095,041; 4,100,367 and 4,122,298, each of which is assigned to the assignee of the present invention.
The insulators must be constructed to be able to snap over an elongated conductor which is to be centrally supported within an outer housing. Thus, the insulators are commonly made in sections which can be snapped together over the central conductor and must have sufficient strength to withstand the force of having the outer housing formed over their outer peripheries in a suitable forming and corrugating apparatus which produces the flexible outer housing. Finally, the insulators must be capable of withstanding the substantial loading forces which are produced when the flexible bus is bent on a radius as when the cable is wound on a reel.
It has been found that insulator designs used in the past can fail at their outer rim during the time the outer enclosure is being corrugated and/or during the time the cable is being bent to load it on a circular reel. Also, after the cable is installed, loads caused by the differential expansion of the central conductor and outer enclosure create forces on the insulators. Thus, the central conductor which is confined by the enclosure tends to get hotter during operation than the outer enclosure and, therefore, expands more than the outer shell. This sets up axial forces throughout the cable, and radial forces could occur in the curved rim sections of the insulators.
It has further been found with present designs that when the insulator fails, it commonly fails either at the latch or keeper areas at which two halves or multiple sections of the insulator are joined together.